If you watch the video of where he said "“I thought it was a mistake on the part of the White House to propose it. I think it was a mistake for Republicans to go along with it,” Romney said in the NBC interview, excerpts of which were provided by the network." As shown in your source is actually him talking about the sequester portion of the debt ceiling deal, where to raise the debt ceiling the Dems and Reps agreed to automatic across the board budget cuts, in ALL areas of government spending, if their newly established "super-committee" on debt didn't produce spending cuts(which they haven't so far because Reps and Dems can't agree).
Mitt Romney has, to his credit, been fairly consistent on his ideas about military spending and proposing not cutting DoD funding any more and to maintain it where it is as a certain percentage of GDP. Defense spending has steadily dropped since Obama entered office, as one can imagine it primarily has to do with the end of the War in Iraq, however it has not dropped in proportional amount to what that war costs. In other words, if the war was costing X per year then the budget has been dropping by Y where Y is far less than X. In fact its only dropped by 31 billion since last year while the Iraq War was costing roughly 150 billion a year
by the time it ended. (Not that money is only DoD money, it doesn't include other government agency's funding spent in or for Iraq)
Romney: GOP leaders made (Actual video of Mitt's quote)
http://comptroller.defense.gov/defbudget/fy2013/FY2013_Budget_Request_Overview_Book.pdf (Page 7 for yearly DoD budget, FY13 budget is only proposed at this time)
http://www.fas.org/sgp/crs/natsec/RL33110.pdf (Page 12 for yearly DoD Iraq budgets)
Budget Control Act of 2011 - Wikipedia, the free encyclopedia
So he's not saying that the USA should have defaulted on our public debt, I'm sure he knows that's the dumbest thing any Congress or President could do and it makes me sick how the Republicans in the House took the issue hostage to force petty political gains and in the process screwed with the meaning of the phrase "Full faith and credit of the United States" on which our whole monetary value and economy is based. By the way Mitch McConnell used the same word, hostage, to refer to his strategy for the debt ceiling debates.
Anyway all Mitt is saying is he's against sequestration for the DoD, personally I'm against sequestration too because its a stupid policy and stupid way to cut the budgets. Its not like the DoD gets X amount of dollars per year to do whatever it thinks is best, most of the DoD's budget is marked for certain projects and can't be spent elsewhere unless Congress changes its mind. So for example I read a story about how Congress has marked enough money to purchase 2 new submarines but if sequestration goes into effect then they will only have enough money for 1.8 submarines? Well how do you buy 1.8 subs? Obviously you can't so what do you do with the .8 left over? Who the hell knows, but technically its marked solely for the purchase of new submarines and the contacts have already been negotiated for the original amount of money given the DoD for those subs.
I'm all for spending cuts, especially in the DoD since Iraq is completely over, but we can be smart about how we do it and not just take the lazy and easy after of just cutting everything by 10% without looking at how it affects anything. We can and should cut certain programs more than others, perhaps eliminate some all together, and make a reasonable transition.
Defense Cuts: How Do You Buy 1.8 Submarines? : NPR
So ya back to the OP, your source sucks because it twists his words to mean something they don't. He's not talking about raising the debt ceiling as being bad he's talking about sequestration, which your article doesn't even mention once.